The invention relates to dental equipment, and more specifically the invention is concerned with a changeable filter for a dental cuspidor. This invention includes modifications and improvements over the filter assemblies described in U.S. Pat. No. 5,571,412, which is hereby incorporated by reference.
Cuspidors for dental operatories are typically fitted with a filter assembly connected to receive the effluent waste (which includes blood and saliva from the dentist's patients) from the cuspidor. The filter typically has a plastic perforated filter screen, designed to remove most solids of significant size, along with blood and other materials associated with the solids. These solids include large particles of amalgam (containing mercury), and the filter prevents them from entering the sewage system. The filter element, generally a basket-shaped element, is usually removed and changed frequently. Originally, cuspidor filters were not disposable and had to be removed and cleaned. More recently, the filter element has been disposable and need not be cleaned, but the task of changing the filter has been one of the most undesirable, distasteful jobs in the dental office, with a great possibility of cross infection, or infecting of the dental office staff.
A conventional filter canister has a canister body, and a lid or cover under which the filter basket is contained. The material from the cuspidor enters the filter canister from below, through one or several inlet tubes, passes through the filter and is discharged through an exit tube at the bottom of the canister, generally drawn by a vacuum.
A conventional dental cuspidor filter canister is formed of a relatively tough but flexible plastic material which is integrally molded to include at least two tube connecting nipples at its bottom side, at least one for entry of liquid and solid material from the cuspidor, and at least one for the filtrate outlet. The canister has a generally cylindrical chamber which receives a basket shaped disposable filter to be dropped in from above. The inlet opening, or, as typically provided, the two inlet openings, have cylindrical collar extensions extending upwardly and vertically disposed inside the chamber, and the filter basket has similarly positioned cylindrical collars which slide down over and fit fairly closely on the inlet collars of the canister. Thus, with the filter basket in place, liquids entering the inlet or inlets will flow up through the filter basket collars and pour out into the canister plenum above the filter mesh, which is at the bottom of the filter basket.
When fully installed, the filter basket sits at a slightly elevated position above the bottom of the canister, such that a small space, e.g. about 1/4 inch, is defined below the filter mesh and above the interior bottom of the canister. This space collects filtrate for exiting through the outlet in the bottom of the canister.
A vertical stem or post typically is formed integrally with the disposable filter basket, positioned in the center of the basket and being the uppermost extension of the filter basket. This stem enables gripping between the thumb and finger of the attendant, for removal and changing of the filter basket. Normally the stem is covered with cuspidor effluent.
At the top of the canister, a cover or lid of similar plastic to that of the canister is provided, often having some form of locking engagement device for securing to the canister, which may require placing the lid on the canister at a certain orientation followed by rotation to lock the lid in place. An O-ring may be included on the lid for sealing against a rim surface on the canister.
It is among the objects of the present invention to make easier and more efficient, and particularly to make less distasteful and safer, relative to cross-contamination and infection of dental staff, the task of changing the filter in a dental cuspidor filter assembly. A further object is to provide a filter structure which allows material (waste) to be disposed of into a waste disposal container, in a contained environment.